netdev - Re: [PATCH net-next v3 2/2] udp: Use hash2 for long hash1 chains in __udp*_lib_mcast

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Message-ID: <1405494787.10255.47.camel@edumazet-glaptop2.roam.corp.google.com>
Date:	Wed, 16 Jul 2014 09:13:07 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	David Held <drheld@...gle.com>
Cc:	netdev@...r.kernel.org, davem@...emloft.net, willemb@...gle.com
Subject: Re: [PATCH net-next v3 2/2] udp: Use hash2 for long hash1 chains in
 __udp*_lib_mcast_deliver.

On Tue, 2014-07-15 at 23:28 -0400, David Held wrote:
> Many multicast sources can have the same port which can result in a very
> large list when hashing by port only. Hash by address and port instead
> if this is the case. This makes multicast more similar to unicast.
> 
> On a 24-core machine receiving from 500 multicast sockets on the same
> port, before this patch 80% of system CPU was used up by spin locking
> and only ~25% of packets were successfully delivered.
> 
> With this patch, all packets are delivered and kernel overhead is ~8%
> system CPU on spinlocks.
> 
> Signed-off-by: David Held <drheld@...gle.com>
> ---

Signed-off-by: Eric Dumazet <edumazet@...gle.com>

Thanks David.

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